The difference between fresh air unit and air handling unit

Fresh Air Unit and Air Handling Unit (AHU) are two different types of air handling equipment, although they overlap in some functions, their design purposes and application scenarios are different.

1. Function and purpose

Fresh air unit:

Main function: Introduce fresh outdoor air and process it before sending it indoors. The core task of a fresh air unit is to improve indoor air quality, provide fresh, oxygen rich air, and discharge indoor exhaust gases and pollutants.

Application scenarios: Commonly used in places where air quality needs to be improved, such as homes, office buildings, schools, etc. Fresh air handling units usually only handle the input of fresh air, so their functions are relatively limited.

Air Handling Unit (AHU):

Main function: Comprehensive air processing, including heating, cooling, humidification, dehumidification, filtration, and mixing of fresh and return air. The air handling unit not only introduces fresh air, but also processes the indoor return air to achieve a comprehensive effect of controlling indoor temperature, humidity, and air quality.

Application scenario: Commonly used in large buildings or industrial places, such as shopping malls, hospitals, factories, etc., environments that require comprehensive air conditioning and treatment. AHU is typically part of an HVAC (Heating, Ventilation, and Air Conditioning) system, responsible for a wide range of air handling tasks.

2. Structure and composition

Fresh air unit:

It mainly consists of fans, filters, heat exchangers, and control systems, with a focus on filtering outdoor air and sending it indoors.

Heat recovery devices can be equipped to improve energy efficiency.

Air handling unit:

The structure is more complex, usually including multiple modules such as fans, filters, heaters, coolers, humidifiers, dehumidifiers, heat exchangers, etc.

AHU can handle a large amount of air and finely adjust temperature, humidity, air quality, etc.

3. Air circulation mode

Fresh air unit:

Generally, only the air introduced from the outside (fresh air) is processed, and the indoor return air is not processed or simply discharged.

Air handling unit:

It handles both the fresh air introduced from the outside and the return air indoors. You can mix fresh air and return air, or handle one type of air independently.

4. Energy efficiency and operation mode

Fresh air unit:

Usually equipped with heat recovery devices to reduce energy loss while introducing fresh air.

High energy efficiency, but relatively limited functionality.

Air handling unit:

Due to the more complex processing flow, energy efficiency depends on device configuration and operating mode.

While providing comprehensive air conditioning, it may consume more energy.

summary

Fresh air handling units are mainly used to introduce and process fresh air, improve indoor air quality, while air handling units are used to comprehensively treat the entire air environment, including temperature, humidity, and air quality regulation. There is some overlap in functionality between the two, but there are significant differences in usage and complexity.